Pig scrapers are used in many applications, particularly including delivery of a liquid through a pipe, line or other conduit, including the delivery of coating material through a flexible conduit. Modern coating systems for the series coatings of construction parts, vehicle bodies and the like utilize pig scrapers to deliver coating material through small diameter flexible plastic conduits and simultaneously scrape and clean the conduits for delivery of different coating materials, such as different color paints, solvents, thinner and the like. Thus, it is important that the pig scraper in such applications maintain sealed contact with the internal surface of the conduit as the pig traverses through the conduit to deliver a liquid coating material and simultaneously scrape and clean the line.
The prior art includes a number of scraper pigs having a flexible frustoconical sealing lip which engages the internal surface of the conduit, cleaning the internal surface of the conduit as the pig traverses the conduit. Reference is made to co-pending application Ser. No. 11/434,411 filed May 15, 2006 of the Applicant, which discloses a pig for bi-directional movement through a conduit of a coating delivery system. The scrapper pig disclosed in this application has a generally cylindrical body portion and two thin flexible resilient frustoconical sealing lips which extend in opposite directions from the central body portion. The sealing lips are resiliently biased against an internal surface of the conduit by the resiliency of the material from which the lips are formed, driving coating material, including paint and other coating materials, solvent or thinner, through the conduit and simultaneously scraping and cleaning the internal surface of the conduit. In a preferred embodiment of the pig disclosed in the above-referenced co-pending application, the outer surface of the flexible sealing lips include a relatively sharp, self-sharpening triangular sealing edge which is resiliently biased against an internal surface of the conduit as the pig traverses back and forth through the conduit, significantly prolonging the life of the pig as further disclosed below. Reference is also made to copending application Ser. No. 11/434,421 filed May 15, 2006 also assigned to the assignee of this application which discloses an alternative embodiment of a scraper pig. The disclosures of both above referenced copending applications are incorporated herein by reference.
However, there has been a long felt need in this art for an improvement in the sealing and scraping action of pigs having flexible sealing lips which is met by the scraper pig of this invention.